SCIENCE NEWS UPDATE – SEPTEMBER 2019

Type 2 diabetes: Good evidence for whole grains and cereal fibre in prevention

An umbrella review of 53 meta-analyses has pulled together the evidence to date on diet and type 2 diabetes incidence – with good news on whole grains and cereal fibre! For both, high-quality evidence points to an inverse association with type 2 diabetes.

The comprehensive review, recently published in the British Medical Journal, looked at the quality of the evidence for the role of dietary factors in the development of type 2 diabetes, including dietary patterns, food groups, foods, and dietary components, such as macro- and micro-nutrients.

Of all the factors assessed, the quality of evidence was rated ‘high’ only for whole grain intake, cereal fibre intake and for a moderate intake of alcohol – all of which were protective. For whole grains, an increment of 30g/day was associated with a 13% risk reduction, and for cereal fibre, an increment of 10g/day was linked with a 25% risk reduction.

On the flip side, high-quality evidence linked higher intakes of red meat, processed meat, bacon and sugar-sweetened beverages with an increased incidence of type 2 diabetes.

The researchers point out that fruit fibre and vegetable fibre were not significantly associated with incidence of type 2 diabetes, suggesting dietary fibre source is important. They add that the beneficial effect of whole grains and cereal fibre could be partly due to their high content of phytochemicals, vitamins and minerals.

Reference:

Neuenscgwander M et al. Role of diet in type 2 diabetes incidence: Umbrella review of meta-analyses of prospective observational studies. BMJ2019;366:12368. https://doi.org/10.1136/bmj.l2368

 

Inflammation: Not all sources of fibre are created equal

A high-fibre diet, made up mainly of whole grain fibre sources, has the greatest impact on reducing inflammatory markers in women above a healthy weight, according to a just-published randomised controlled trial.

Researchers randomly assigned 75 women to three diet groups: a ‘whole grain diet’ group, a ‘fruit and vegetable diet’ group, and a combined ‘whole grain, fruit and vegetable diet’ group for 10 weeks. They looked at inflammation indices at baseline and again at the end of the trial.

All three groups consumed 35g fibre a day, but the proportions of the foods contributing this fibre differed.

Each of the three diet groups showed significant beneficial changes in serum inflammatory biomarkers (CRP, TNF-α, IL-6, D-dimer, and serum fibrinogen) after 10 weeks, but the most notable changes were among those following a diet higher in whole grain derived fibre.

The reason for these differences are not yet known. But the researchers suggest the unique interplay between the gut microbiota and whole grain specific polyphenols may help explain the positive impact of a diet rich in whole grains. Watch this space!  

Reference:

Arabzadegan N et al. Effects of dietary whole grain, fruit, and vegetables on weight and inflammatory biomarkers in overweight and obese women. Eat Weight Disorder2019. [Epub ahead of print]. https://doi.org/10.1007/s40519-019-00757-x

 

Heart disease: Skipping breakfast linked with an increased risk

A first-of-its-kind meta-analysis of epidemiological studies has concluded that skipping breakfast is linked with a significantly increased risk of heart disease.

In pooling the outcomes of eight studies, involving more than 284,000 people, the researchers suggest a 24% increased risk of heart disease between adults who ‘most skip’ brekkie, and ‘least skip’ it (first quartile, compared with the fourth quartile).

The researchers, who published their findings in the American Journal of Cardiology, suggest a number of physiological mechanisms could help explain the findings.

They say skipping breakfast may disrupt the body’s circadian rhythm or ‘body clock’, impacting cardiometabolic risk factors, and going without breakfast may also mean overeating later in the day, with knock-on effects to body weight, insulin resistance, and blood pressure and serum lipid levels. 

The results are supported by a new systematic review of prospective cohort studies, by Australian researchers.

The pooled data from this review suggests that people who regularly skipped brekkie were around 21% more likely to experience cardiovascular disease or die from it than people who regularly had breakfast. The risk of all-cause death was 32% higher in people who regularly skipped breakfast. 

References:

Takagi H et al. Meta-analysis of relation of skipping breakfast with heart disease. Am J Cardiol2019;00:1-9. https://doi.org/10.1016/j.amjcard.2019.06.016

Ofori-Asenso R et al. Skipping breakfast and the risk of cardiovascular disease and death: A systematic review of prospective cohort studies in primary prevention settings. J Cardiovasc Dev Dis. 2019;6(3):30. https://doi.org/10.3390/jcdd6030030

 

Cognitive decline: A role for whole grains and vitamin B6 in prevention

Dietary intake of vitamin B6 and whole grains has been directly associated with better cognitive function, according to new US research.

The prospective cohort study tracked 516 young adults (mean age: 32.03 ± 5.96 years at baseline) into midlife (mean age: 49.03 ± 4.86 years at follow-up), and collected data on dietary intake and cognitive function.

Dietary intake of vitamin B6 and whole grains in young adulthood was linked with better cognitive function in midlife, after taking into account age, race, sex, and total energy (calorie) intake. On the other hand, processed meat and foods fried at home were consistently inversely associated with cognitive function.

When it comes to whole grains, most Australian adults (70%) fall short of the recommended target of 48g a day.

According to the Australian Institute of Health and Welfare, dementia was the second leading cause of death in Australia in 2017, and is expected to affect up to 550,000 Australians by 2030. Their latest burden of disease report also states that a diet low in whole grains and high fibre cereals is the leading dietary risk contributing to the total burden of disease in Australia.

Reference:

Fortune NC et al. Dietary intake and cognitive function: Evidence from the Bogalusa Heart Study. AJCN2019;109(6):1656-63. https://doi.org/10.1093/ajcn/nqz026

 

Four weeks of oats for brekkie alleviates markers of inflammation and oxidative stress

Good news for oat lovers! New research has found daily consumption of 70g (~¾ cup) of oats, containing 3g β-glucan, reduced markers of inflammation and oxidation in adults with high blood lipids, after just four weeks.

The randomised crossover study also found LDL- and total-cholesterol decreased, by 10% and 5%, respectively.

Hypercholesterolemic adults (aged 30-60 years) were randomly assigned to consume either instant oat flakes or instant white rice flakes, both made into porridge, daily for four weeks. After this time, they were switched to alternate intervention arms for another four weeks.

Compared to baseline, levels of the inflammatory markers hsCRP, IL-6, IL-8, and TNF-α were significantly decreased after daily consumption of oat porridge, while levels of the antioxidant capacity markers, ORAC and FRAP, increased.

Antioxidant phytochemicals found in oats, including a unique group of phenolic compounds called avenanthramides, decrease inflammation and oxidative stress, and β-glucan, a well-known component of oats, also has a role in reducing inflammation and lipid peroxidation.

Note: This research was supported by PepsiCo Thailand.

Reference:

Pavadhgul P et al. Oat porridge consumption alleviates markers of inflammation and oxidative stress in hypercholesterolemic adults. Asia Pac J Clin Nutr2019;28(2):260-65. https://doi.org/10.6133/apjcn.201906_28(2).0008

 

Whole grain intake linked with less abdominal obesity over 18 years of follow up

Eating more whole grains may be linked with a healthier longer-term waist circumference, according to a large prospective study that involved 18 years of follow up.

Researchers examining data from the Framingham offspring cohort grouped participants into quartiles, based on their whole grain intake (≤8g/day, 8-16g/day, 16-24g/day, and 24+g/day).

They found that a greater whole grain intake was associated with less four-year gain in waist circumference, with those in the highest quartile of whole grain consumption gaining (mean ± SE) 1.77 ± 0.08cm around the middle, compared to 2.86 ± 0.12cm in the lowest quartile.

On the other hand, greater refined grain intake was associated with greater four-year gain in waist circumference, which is a surrogate marker of abdominal obesity.

The researchers concluded that replacing refined grain foods with whole grain equivalents may reduce abdominal weight gain – a risk factor for metabolic and cardiovascular diseases, independent of body weight.   

Note: This research was supported by General Mills Bell Institute of Health and Nutrition.

Reference:

Sawicki C. Whole Grain Intake Is Prospectively Associated with Lower Gain in Abdominal Obesity over 18 Years of Follow-up. Curr Dev Nutr2019;3.Issue Suppl 1. https://doi.org/10.1093/cdn/nzz039.OR33-04-19

 

Gut health: Even small increases in cereal fibre beneficial

A first-of-its kind systematic literature review (SLR) of 40 papers, published over the past 20 years, and involving more than 1,300 people in total, showed intact cereal grain fibres increase gut microbiota diversity and/or abundance, with effects apparent from 24 hours to 52 weeks.

The research found even small increases in wheat fibre, as low as 6-8g/day*, were enough to impact the make-up of the gut microbiota. The strongest evidence was found in the role of wheat bran and wholegrain wheat fibre, which demonstrated the most consistent prebiotic effects on gut microbiota composition.

Previous SLRs in this area have largely focussed on supplemented, isolated fibre types (rather than intact cereal grain fibres, like those consumed in everyday foods such as brekkie cereals and bread) or have explored specific conditions, such as irritable bowel syndrome.

The researchers concluded: ‘Increasing cereal fibre consumption should be encouraged for good overall health and for gut microbiota diversity’ and suggest people make simple dietary changes, such as choosing breakfast cereal rich in wheat bran and whole grain wheat or rye breads.

* An average 40g serve of ready-to-eat cereal, muesli or oats contains around 4g of fibre, with some higher-fibre options containing around 13g a serve. When it comes to bread, two slices of wholegrain/wholemeal bread contain an average of 5g of fibre.

Reference:

Jefferson A, Adolphus K. The effects of intact cereal grain fibers, including wheat bran on the gut microbiota composition of healthy adults: A systematic review. Front Nutr 2019. https://doi.org/10.3389/fnut.2019.00033

 

Diet and CVD risk: Review of evidence from meta-analyses

A recent review of 16 meta-analyses sheds more light on the links between dietary componentsand the risk of CVD and all-cause mortality – with good news for lovers of grains, nuts and veges!

Among the findings, whole grain brekkie cereals were associated with a 16% reduced risk of CVD (based on two studies which looked at this), and bran a 15% reduced risk (also from two studies). When it came to risk of all-cause mortality, both whole grain brekkie cereals (two studies) and oats/oatmeal (one study) were associated with a 12% reduced risk.

The researchers conclude that nuts, whole grain foods, and certain types of vegetables (such as green leafy vegetables) appear to be beneficial for CVD, while processed meat appears to be harmful.

Some of the food items which showed no association of benefit or harm may actually impact on individual cardiovascular risk factors, such as blood pressure or cholesterol levels, say the researchers. And they highlight that overall diet really is key.

Reference:

Kwok CS, Gulati M, Michos ED, Potts J, Wu P, Watson L et al. Dietary components and risk of cardiovascular disease and all-cause mortality: A review of evidence from meta-analyses. Eur J Prev Card2019. https://doi.org/10.1177/2047487319843667

 

Diet and colorectal cancer in UK Biobank: Prospective study

After tracking the diets of nearly half a million UK adults, aged 40-69 years, over an average of almost six years, researchers found those with the highest intake of fibre from breakfast cereals and bread had a 14% lower risk of colorectal cancer (highest fifth of intake, compared with the lowest fifth). The research also found an increased risk for greater red meat and alcohol intake.

In line with the conclusions from another meta-analysis on fibre and colorectal cancer, the researchers state only fibre from cereals, but not fruit and vegetables, was inversely associated with risk.

They say different types of fibre may have different effects on stool transit time and weight – and this may explain the different associations with colorectal cancer. And as intake of fibre from cereals is linked with whole grain intake, phytochemicals or other non-fibre components of whole grains could be responsible for the association, say the researchers.

According to Bowel Cancer Australia, Australia has one of the highest rates of bowel cancer in the world, with more than 15,600 Australians diagnosed with this common type of cancer each year.

References:

Bradbury KE, Murphy N, Key TJ. Diet and colorectal cancer in UK Biobank: A prospective study. Int J Epidemiol 2019. https://doi.org/10.1093/ije/dyz064

Aune D, Chan DS, Lau R et al.  Dietary fibre, whole grains, and risk of colorectal cancer: Systematic review and dose-response meta-analysis of prospective studies. BMJ2011. https://doi.org/10.1136/bmj.d6617

 

Consuming a high-fibre cereal helps gastrointestinal symptoms during Ramadan

A new randomised controlled trial has found eating a high-fibre cereal at dawn during Ramadan is linked with higher satiety rating scores, improved bowel habits, reduced bloating frequency, and improved total and LDL cholesterol.

The researchers randomised 81 study participants, aged 18 to 47 years, to consume either 90g of high-fibre cereal (11g fibre/90g) at dawn (right before fasting) over 20 days, or to maintain their habitual diet intake.

High-fibre cereal consumption resulted in reduced bloating frequency, and improvements in bowel movements – important findings, say the authors, given that constipation is the most frequent gastrointestinal symptom experienced by the end of Ramadan.

Both the control and intervention groups showed a reduction in weight and BMI at the end of the 20-day study period, but there were no significant differences in body weight, percentage body fat, waist circumference and BMI between the two groups. 

Reference:

Jarrar AH, Beasley JM, Ohuma EO et al. Effect of high fiber cereal intake on satiety and gastrointestinal symptoms during Ramadan. Nutrients2019. https://doi.org/10.3390/nu11040939

 

Of 12 food groups, low whole grain intake found to impact health the most

Suboptimal intakes of 12 major food groups were associated with 45-59% of total disability-adjusted life years from coronary heart disease, stroke, type 2 diabetes and colorectal cancer, across 16 European countries, according to new research.

Of the 12 food groups, a suboptimal intake of whole grains had the biggest impact – followed by nuts, processed meat, fruit, fish, legumes and sugar-sweetened beverages. The researchers say improving intake of whole grains and nuts should be a priority from a public health point-of-view.

This echoes comments from the authors of a major study published this year in The Lancet, which found more than half of diet-related deaths in 2017 were due to the three leading risk factors: high intake of sodium, low intake of whole grains, and low intake of fruits.

The authors of this study concluded: ‘Findings suggest that dietary policies focussing on promoting intake of components of diet for which current intake is less than the optimal level might have a greater effect than policies only targeting sugar and fat’.

References:

Schwingshackl L, Knüppel S, Michels N, Schwedhelm C, Hoffman G, Iqbal K et al. Intake of 12 food groups and disability-adjusted life years from coronary heart disease, stroke, type 2 diabetes, and colorectal cancer in 16 European countries. Eur J Epidemiol2019. https://doi.org/10.1007/s10654-019-00523-4

Diet Collaborators. Health effects of dietary risks in 195 countries, 1990–2017: a systematic analysis for the Global Burden of Disease Study 2017. The Lancet2019. https://doi.org/10.1016/S0140-6736(19)30041-8

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